The invention pertains to a radionuclide generator of the parent-daughter type. The generator comprises a column which contains an adsorbant material which acts as a support for the parent nuclide with an inlet and outlet opening connected to inlet and outlet lines. To wash out (elute) at least one desired redioactive substance from the generator a washing solution (eluant) is introduced into the inlet line and the washing solution charged with the desired radioactive substance (eluate) emerges at the outlet line.
The use of radionuclides for the diagnosis and treatment of various medical conditions is widespread. However, some radioactive isotopes have an extremely short half life, so that their use may not be practical because of the time required to transport the material from the location of manufacture to the physician performing the treatment. For medical reasons, however, it is often desirable to use precisely these shortlived isotopes in nuclear medicine, in order to avoid prolonged radiation exposure of the patient. For example the technetium isotope .sup.99m Tc with its relatively short half life of about 6 hours is widely used in scanning and visualizing various organs in the body. Because of its short half life the physiological damage which may result from the use of radionuclides is largely eliminated or at least minimized.
In order to prepare such short-lived radionuclides for the physician, radionuclide generators of the type described above are known; see for example, U.S. Pat. No. 4,041,317, in which the generator column is formed as a hollow cylinder with a circular cross section and a vertical axis. In the area of the upper end of this generator column, the inlet opening is provided with an appropriate inlet line for the rinse solution (eluant). The generator column is provided with an adsorbant material, for example aluminum oxide (alumina), which is a support medium for the parent nuclide of the desired radionuclide. If, for example, .sup.99m Tc is selected as the daughter nuclide for the medical treatment as mentioned above, the molybdenum isotope .sup.99 Mo is used as the parent nuclide. By introducing the rinse solution into the generator column containing the parent nuclide (e.g., .sup.99 Mo), the daughter nuclide (e.g., .sup.99m Tc) is eluted from the generator. The solution thus obtained, with the desired daughter nuclide, is called the eluate.
In order to achieve the greatest possible efficiency, i.e., the cleanest separation, in elution of a desired daughter nuclide, it is desirable to provide the longest possible path for the eluant to travel through the material onto which the parent nuclide is adsorbed. However, when known elongated generator columns are used, considerable problems in the shielding of the column arise. In order to fulfill the radiation protection specifications for an elongated generator column, the shielding (usually lead) must be similarly long, in order to guarantee the necessary adsorption length for the radiation to be held back at each point. The amount of material provided for shielding in the case of such a design (i.e., elongated columns) is greater the longer the generator column is in comparison to its diameter. On the other hand, it is desirable, in order to facilitate handling and transport, to keep the total weight of the radionuclide generator (to which the shielding is the principal contributor) as small as possible.